1. Field of the Invention
The present invention relates to a vacuum cleaner, and more particularly to a multi-cyclone dust collecting apparatus wherein a plurality of cyclone dust collecting apparatuses are in parallel arranged.
2. Description of the Related Art
Generally, a cyclone dust collecting apparatus rotates drawn-in air at a high speed to separate and collect contaminants from the air. The cyclone dust collecting apparatus can be almost permanently used, however, is inferior to a cyclone dust collecting apparatus using dust bag or dust filter in collecting minute dust. Accordingly, a multi cyclone dust collecting apparatus capable of collecting minute dust has been developed.
A multi cyclone dust collecting apparatus comprises a first cyclone part and a second cyclone part, the first cyclone part first separates large contaminants, and then the second cyclone part centrifugally separates the air cleaned from the first cyclone part to collect minute dust. The multi cyclone dust collecting apparatus is superior to a conventional cyclone dust collecting apparatus in collectivity of minute dust.
However, if the multi cyclone dust collecting apparatus is applied, an air passage is complicated in a collecting apparatus such that load of a vacuum suction source increases and air flow noise generates. Particularly, air cleaned from the second cyclone part forms a rotation stream to be discharged via a discharge pipe provided in the second cyclone part by an inertia force of the rotation stream. At this time, the air discharged from the discharge pipe hits the interior surface of the discharge pipe, or collides with the air discharged from the second cyclone part to form turbulence and causes a pressure loss in the discharge pipe. The pressure loss increases load of a suction source and power consumption.
WO 02/267755A1 filed on Sep. 6, 2002 is an example of the multi cyclone dust collecting apparatus. In the WO 02/067755A1, the second cyclone part has a centrebody in a discharge pipe to reduce pressure loss of the discharge pipe. The centrebody, however, blocks a center portion of the discharge pipe such that contaminants such as hair often obstruct the discharge pipe.
A discharge pipe of the second cyclone part having a centrebody is smaller than a discharge pipe in cross section such that current speed of air passing the discharge pipe increases. The stiff increase of current speed of discharged air generates air flow noise in the discharge pipe and operation noise of a cyclone dust collecting apparatus also increases.